The area of cold mill production has, for some time, required on-line gaging equipment that responds quickly and gives accurate results. This requirement has been heightened recently by attempts at cost reduction and economic cold mill production programs. Steel producers have found one area (cold mill production) in which "extra" give-aways to the customer can be alleviated or merely reduced, resulting in surprising cost reduction and increased mill production efficiency. These "give-aways", which are basically extra product sent to the customer in order to insure he gets at least what he has ordered, are predicated upon an uncertainty in footage of product or product weight and/or product gage. If the mill operator could find a more exact way of determining these parameters, there could be a reduction in the amount of steel product with confidence that the customer will not be "short-changed".
Since the first gaging devices were installed within cold reduction mills to the present sophisticated radiation absorption devices (such as X-rays and Accuray gages) on-line instantaneous gaging has been desired. Operating experience has shown, however, that the new equipment, like the old equipment, can be subject to gross and costly errors due to instrument drift and equipment malfunctioning. In response to this basic defect, some method of checking average product gage has been necessary. Current practice in this regard continues to be the "Wrap Check Average Gage Method".
The present "Wrap Check Average Gage Method" of checking the accuracy of the on-line cold mill gaging equipment is accomplished manually on solely a random basis. This task is performed by inserting markers into the side wall of a coil being rolled with a known number of wraps between the markers. After the coil has been completely rolled, the distance between the markers is measured and divided by the number of wraps between the markers. This method, while cumbersome, is accurate if care is taken in inserting the markers, measuring the distance therebetween, and calculating the end result. This method, however, does have major disadvantages, i.e. (1) gage results are not available until the coil being "tested" has been completely rolled; (2) the results obtained represent only the average gage for that portion of the coil lying between the two markers inserted in the coil; (3) the results can be no better than the measurements taken to calculate the average gage--the factor of human error; and (4) the method is extremely hazardous to the operator inasmuch as he must open the safety enclosure surrounding the moving coil to insert the markers.
It should be apparent that the present manual calculation method leaves much to be desired. Additionally, there would appear to be some degree of dissatisfaction with the modern expensive gaging systems which are subject to drift and slippage errors. The present dynamic gage-averaging method and apparatus is a successful attempt to fill this void.